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B What does plus/minus mean?

  1. Feb 12, 2019 at 11:09 PM #1
    Not sure if this is the right "forum section" but what does "±" mean when it comes to writing a lab report? I don't remember this back in high school but idk.
     
  2. jcsd
  3. Feb 12, 2019 at 11:56 PM #2

    symbolipoint

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    That symbol means, "plus or minus".
    Also it can be read, "The positive or the negative of...".
     
  4. Feb 13, 2019 at 12:20 AM #3

    fresh_42

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    ##y= \pm \sqrt{x}## means, that both possible values are considered, e.g. in ##x_{1,2} = -\dfrac{p}{2} \pm \sqrt{\left( \dfrac{p}{2} \right)^2-q}\,.## So it's ##x_1=-\dfrac{p}{2} - \sqrt{\left( \dfrac{p}{2} \right)^2-q}## and ##x_2=-\dfrac{p}{2} + \sqrt{\left( \dfrac{p}{2} \right)^2-q}\,.##

    ##G = (6.674 08 \pm 0.000 31) \cdot 10^{-11} \,\dfrac{m^3}{kg \cdot s^2}## means, that the gravitational constant isn't known exactly but only up to a certain amount of significant digits. It is around ## 6.674 08 \cdot 10^{-11} \,\dfrac{m^3}{kg \cdot s^2}## but possible values range between ##6.673 77 \cdot 10^{-11} \,\dfrac{m^3}{kg \cdot s^2}## and ##6.674 39 \cdot 10^{-11} \,\dfrac{m^3}{kg \cdot s^2}\,.## Of course there is only one exact value, but we currently cannot measure it better than within this range.
     
  5. Feb 13, 2019 at 2:40 PM #4

    davenn

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    WOW could you make it any more difficult ??
    it was a B level question :eek:



    Yes

    so for example ....
    I have a result of 50 ± 5 that is a result that is somewhere between 45 and 55 so the mid point is noted with the error margin
    or I have a result of 100 ± 10% again the same thing but this time you are stating a percentage error margin

    would be two easy examples of it's use


    Dave
     
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